In general, a compressor is a mechanical apparatus that receives power from a power generation apparatus such as an electric motor, a turbine or the like and compresses air, refrigerant or various operation gases to raise a pressure. The compressor has been widely used in electric home appliances such as a refrigerator and an air conditioner, or in the whole industry.
The compressors are roughly classified into a reciprocating compressor wherein a compression chamber to/from which an operation gas is sucked and discharged is defined between a piston and a cylinder and refrigerant is compressed as the piston linearly reciprocates inside the cylinder, a rotary compressor which compresses an operation gas in a compression chamber defined between an eccentrically-rotated roller and a cylinder, and a scroll compressor wherein a compression chamber to/from which an operation gas is sucked and discharged is defined between an orbiting scroll and a fixed scroll and refrigerant is compressed as the orbiting scroll rotates along the fixed scroll.
Although the reciprocating compressor is excellent in mechanical efficiency, its reciprocating motion causes serious vibrations and noise problems. Because of this problem, the rotary compressor has been developed as it has a compact size and demonstrates excellent vibration properties.
The rotary compressor is configured in a manner that a motor and a compression mechanism part are mounted on a drive shaft in a hermetic container, a roller fitted around an eccentric portion of the drive shaft is positioned inside a cylinder that has a cylinder shape compression chamber therein, and at least one vane is extended between the roller and the compression chamber to divide the compression chamber into a suction region and a compression region, with the roller being eccentrically positioned in the compression chamber. In general, vanes are supported by springs in a recess of the cylinder to pressurize surface of the roller, and the vane(s) as noted above divide(s) the compression chamber into a suction region and a compression region. In general, vanes are supported by springs in a recess of the cylinder to pressurize surface of the roller, and the vane(s), as noted above, divide(s) the compression chamber into a suction region and a compression region. The suction region expands gradually with the rotation of the drive shaft to suck refrigerant or a working fluid into it, while the compression region shrinks gradually at the same time to compress refrigerant or a working fluid in it.
In such a conventional rotary compressor, the eccentric portion of the drive shaft continuously makes a sliding contact, during its rotation, with an interior surface of a stationary cylinder where the roller is secured and with the tip of the vane where the roller is also secured. A high relative velocity is created between constituent elements making a sliding contact with each other, and this generates frictional loss, eventually leading to degradation of compressor efficiency. Also, there is still a possibility of a refrigerant leak at the contact surface between the vane and the roller, thereby causing degradation of mechanical reliability.
Unlike the conventional rotary compressors subject to stationary cylinders, U.S. Pat. No. 7,344,367 discloses a rotary compressor having a compression chamber positioned between a rotor and a roller rotatably mounted on a stationary shaft. In this patent, the stationary shaft extends longitudinally inwardly within a housing and a motor includes a stator and a rotor, with the rotor being rotatably mounted on the stationary shaft within the housing the roller being rotatably mounted on an eccentric portion that is integrally formed with the stationary shaft. Further, a vane is interposed between the rotor and the roller to let the roller rotate along with the rotation of the roller, such that a working fluid can be compressed within the compression chamber. However, even in this patent, the stationary shaft still makes a sliding contact with an interior surface of the roller so a high relative velocity is created between them and the patent still shares the problems found in the conventional rotary compressor.
Meanwhile, WO2008/004983 discloses another type of rotary compressors, comprising: a cylinder, a rotor mounted in the cylinder to rotate eccentrically with respect to the cylinder, and a vane positioned within a slot which is arranged at the rotor, the vane sliding against the rotor, wherein the vane is connected to the cylinder to transfer a force to the cylinder rotating along with the rotation of the rotor, and wherein a working fluid is compressed within a compression chamber defined between the cylinder and the rotor. However, these rotary compressors require a separate electric motor for driving the rotor because the rotor rotates by a drive force transferred through the drive shaft. That is, when it comes to the rotary compressor in accordance with the disclosure, a separate electric motor is stacked up in the height direction about the compression mechanism part consisting of the rotor, the cylinder and the vane, so the total height of the compressor inevitably increases, thereby making difficult to achieve compact design.
Moreover, rotary compressors require lubrication to reduce frictional force and frictional heat between members that make a sliding contact while rotating. In a conventional compressor, the roller and the cylinder are typical members making a sliding contact so an interior of the compression chamber had to be lubricated, and this made it unavoidable the mixing of refrigerant and lubricating oil. On account of this, an accumulator had to be installed additionally to separate the refrigerant from the lubricating oil, which required extra large compressors and became the leading cause of manufacturing cost.
Besides, in case the electromotive mechanism and the compression mechanism are connected with a drive shaft and laminated in the height direction, an oil pump and an oil feed passage had to be provided additionally. Also, with the approach of pumping up the lubricating oil stored at the bottom of the interior of the housing and then scattering the oil upward to feed it to the compression mechanism, the lubricating oil could not be distributed evenly over the sliding contact portions.